1. Field of the Invention
The present invention relates to a radiation detection device, a radiographic image capture device, a radiation detection method and program storage medium, and in particular to a radiation detection device, a radiation detection method and program storage medium that detects initiation of irradiation of radiation, and a radiographic image capture device that captures a radiographic image expressing radiation passed through a subject.
2. Description of the Related Art
Recently, radiation detectors such as Flat Panel Detectors (FPDs) are being implemented in which a radiation sensitive layer is disposed on a Thin Film Transistor (TFT) active matrix substrate and with which radiation can be converted directly into digital data. Radiographic image capture devices that employ such radiation detectors and can capture radiographic images expressing irradiated radiation are also being implemented. Radiation conversion methods used by radiation detectors employed in such radiographic image capture devices include indirect conversion methods, in which radiation is first converted into light with a scintillator and then the converted light is converted into electric charge with a semiconductor layer such as a photodiode, or direct conversion methods in which radiation is converted into electric charge with a semiconductor layer such as amorphous selenium. There are various materials that may be used in the semiconductor layer for each method.
In such radiographic image capture devices, if the radiographic image capture device itself can detect states such as initiation of radiation irradiation, termination of radiation irradiation, and an irradiated amount of radiation, it becomes unnecessary to connect an image capture control device (referred to as a console) that performs overall control of the radiographic image capture device and the radiation source to the radiation source. Such a configuration is preferable from the perspective of simplifying the system configuration and simplifying control by the image capture control device.
A radiation detection method utilizing a histogram is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 2011-177356 as technology related to such types of radiographic image capture devices capable of detecting the irradiation state of radiation. In this technology, initiation of radiation irradiation is determined based on a frequency distribution of difference data obtained by voting difference data between data of adjacent radiation detection elements on a detection section onto a single histogram for each frame.
However, in the technology disclosed in JP-A No. 2011-177356, since radiation is detected by employing difference data between data for adjacent radiation detection elements, the value of the difference data gets smaller as the irradiation amount of radiation gets smaller. Therefore, in this technology the detection precision of radiation decreases as the irradiation amount of radiation gets smaller.